Control instrument



Sept. 13, 1949. E. c. BURDICK 2,481,320

CONTROL INSTRUMENT Filed June 22, 1944 4 Sheets-Sheet 1 Hi'iwmw l' INVENTOR. EDWIN C. BURDICK Sept. 13, 1949. E. c. BURDICK 2,481,820.

CONTROL INSTRUMENT F iled June 22, 1944 4 Shets-Sheet 5 FIGS an;agggggggggimnnm X llllIIlllll mmvron. EDWIN q. BURDICK ATTORNEY.

Sept. 13, 1949. E. c. BURDICK CONTROL INSTRUMENT 4 Sheets-Sheet 4 Filed June 22, 1944 FIG. IO

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- 1 INVENTOR. EDWIN C.BURDI CK Patented Sept. 13, 1949' OFFICE CONTROL INSTRUMENT Edwin C. Burdlck, Philadelphia, Pm, assignor, by,

mesne assignments, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation 01' Delaware Application June 22, 1944, Serial No. 541,510

7 Claims. (Cl. 236-74) The general object of the present invention is to provide a control instrument of the type comprising an element deflecting in accordance with variations in a controlling quantity, with improved means for effecting control actions on and in accordance with the deflection of said element.

A specific object of the present invention is to provide a control instrument of the type specified, with improved means for adjusting the instrument control point, i. e., for varying the value of the controlling condition at which a control action is effected.

Another specific object of the invention is to provide means for varying the magnitude of the movement given an instrument controlling element by a given change in the magnitude of the controlling quantity, accordingly as the value the latter does or does not approximate a predetermined control point value of the quantity.

A further object of the invention is to provide a simple and compact control instrument of the general character specified comprising one or more electronic valves each associated with means for causing the valve to oscillate or not to oscillate, dependent on the value of the controlling condition, and means for effecting control actions in response to changes in the current flow through the valve.

My improved instrument is characterized by its mechanical simplicity and compactness and its high sensitivity and capacity for use in effecting "on-off control adjustments and multi-position step adjustments in response to very small changes in the value of the controlling condition. The invention is well adapted for use in effecting adjustments of a control valve or switch in response to variations in a controlling condition which may be a temperature, a pressure, a velocity or some other physical condition or quantity subject to measurable changes in making compensating or corrective control actions desirable.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages, and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of the invention.

7 Fig. 1 is an elevation of a control instrument;

Fig. 2 is a section on the line 2.-2 of Fig. 1;

Fig. 3 is a view taken at right angles to Fig. 2;

Fig. 4 is an inverted plan of parts shown in F18. 6;

Fig. 5 is a diagram illustrating a control system in which use is made of the instrument shown in Fig. 1;

Fi 6 shows a modification of parts-shown in Fig. 1;

Fig. 7 is an inverted plan of parts shown in Fig. 6;

Fig. 8 is a, view taken at right angles to Fig. 6;

Fig. 9 is a diagram illustrating a control system in which use is made of the instrument features shown in Figs. 6, '7 and 8;

Figs. 10 and 11 are different fragmentary elevations of a modified form of control point adlusting mechanism;

Fig. 12 is a view of a portion of Fig. 10,- from the left of that figure;

Fig. 13 is a top view of a portion of an actuating lever; and

Fig. 14 is a view taken similarly to Fig. 11 illustrating a modification.

In Figs. 1-5 I have illustrated the use of a desirable form of the present invention in a recording control instrument Ill comprising an element ll deflected by movements of the free end of a Bourdon tube spiral l2 having its other end anchored to the instrument casing. Fluid pressure is transmitted by a tube or capillary Hi from a source of variable pressure ll, which may be, and, as shown, is, the bulb of a fluid pressure thermometer responsive to a furnace temperature, or other temperature measured by the instrument.

Through a lever and link arrangement the deflecting arm ll oscillates an element l5 about an axis l6 and gives longitudinal adjustments to a link l1, through which the instrument control mechanism is directly adjusted. Except in respect to its control point adjustment provisions, the form of said lever and link arrangement constitutes no part of the present invention.

As shown, the oscillating element 15 is con-' nected through a link l8 to the arm ll. Another arm I9 01' the element 15 is connected by a link 20 to one end of a floating lever 2 I. The latter is pivotally connected at its opposite end to an adjustable fulcrum member 22. The latter is pivotally connected to the instrument framework to turn about the axis l6 and is provided at its outer end with a curved extension 23 having a concave inner edge 24 which extends circularly about the axis l6 and is knurled. The knurled edge 24 is engaged by a knurled roller element 25 having shaft extensions 25' journalled in a spring support 28. The latter is shown as a spring arm having one end secured to the instrument casing and having its other end bifurcated and provided with bearings for the shaft extensions A hand wheel, or knob 21 secured to one of the shaft extensions 25' forms a means for rotating the member 25. Through the engagement of the knurled periphery of the member 25 with the knurled edge 24 of the member 22 the latter is rotated about the axis l6 when the member 25 is rotated.

The upper end of the control link element i? is pivotally connected to the floating lever 2| intermediate the ends of the latter, and the eflect of the angular adjustment of the member 22 is a control point adjustment of the control apparatus. The well known effect of such a control point adjustment is to vary the normal value of the. temperature or other controlling condition which the instrument tends to maintain. Or-

dinarily, and as shown, the member 22 includes or gives motion to an index arm 28 which indicates the value of the quantity measured and controlled on the scale formed by the lines on the record chart 98 on which a curve showing the varying value of the quantity measured is traced by the pen arm 29 connected to and turning with the oscillating member I5. As shown, the chart 88 is a circular chart clamped to a chart shaft 3i normally rotated at suitably slow speed by a clock motor (not shown) which may be of any usual form.

In the instrument shown in Fig. 1, the longitudinal adjustments of the control link member produced by pressure variations in the thermometer bulb M, oscillate a controlling vane element about a pivot 36. In the preferred construction shown, pivot 86 is carried by a control mechanism casing 37 attached to the back wall of the casing of the instrument ill by screws 38. As shown the vane element 35 supports a vane 68 in the form of a thin arcuate plate of aluminum, copper or other electrically conductive metal, the plane of the vane being perpendicular to the pivot 36. The vane element includes a weight 4| adjustable to balance the vane element against gravitational bias. The body portion of the vane element is formed with an elongated slot 42 extendin radially away from the pivot 36 and receiving a pin 43 carried by the arm 44 of an oscillating element mounted on a pivot 45 and including a second arm 46. The pivot 45 is carried by the casing element 81 and is parallel to the pivot 36. The previously mentioned link I1 is connected to the arm 46.

The arm 44 carries a counterweight 4'| adjustable to balance the parts including the arm 44 oscillating about the pivot 45 against gravitational bias.

In the instrument shown in Figs. 1-5, the vane 48 coacts with control coils 48 and 49 to produce control actions as hereinafter described. The control coils '48 and 49 are carried by spaced apart coil supports 50 adjustably secured on a post or projecting portion 5| of the casing 31 by clamping screws 52. Advantageously, each of the control coils 48 and 49 is a flat spiral, and is separated from the other by a kerf-like space. but little thicker than the vane 40. Each coil advantageously comprises only a few, for example 53/2, convolutions. The. control coils 48 and 49 and their supports 50 need not be illustrated and described in detail herein, as their precise construction forms no part of my invention and they were invented by William H. Wannamaker, and are claimed in his application, Serial No. 541,575, filed June 22. 1944. That application also discloses and claimswarioua control system combinations of control cells and a controlling vane, one of which is shown by way of illustration and example in Fig. 6.

In Fig. 5, the 'coils 48 and 49 'and vane48 are included in a reactive coupling which controls the operation of an electronic grid valve. The latter is enclosed in a duplex tube 55, shown as of the type known as a rectifier beam power amplifier tube, 117 N7 GT. The grid valve a in the tube 55 is a tetrode, comprising a cathode 56, control grid 51', screen grid 56, and anode 59. The tube 55 also encloses a diode valve a including a cathode 68 and. an anode 6|. The cathodes 58 and 68 are heated by a filament .62, connected by conductors 63 and 66 to alternating current supply conductors 64 and 65. The conductor 68 also connects the anode 6| to the supply conductor 64. The grid valve anode 56 and diode cathode 68 are connected by a conductor 6?, a shielded choke coil 58 and a conductor 89. The cathode 56 is connected by a conductor 16 to one terminal of one coil H of a differential relay 12 which has its second terminal connected to the previously mentioned nected in series between condensers l6 and I7.

The condensers 16 directly connects the coil 48 to the conductor 69 and thereby to the anode 59, while the condenser 11 directly connects the coil 49 to the control grid 5?. The control grid is also connected by a high resistance 18 to the conductor 10 and thereby to the cathode 56. The cathode 55 is also connected through the conductor l8 and a condenser 18 to the conductor 61 and the latter also connects the screen grid 58 to one terminal of the choke coil 68 and through the coil 68 to the anode 59. A condenser 88 connects the conductors 66 and 61 and thereby insures direct current energization-of the tetrode valve in the tube 55.

The terminals of the coils 48 and 49 respectively connected to the condensers I6 and I1, are connected to one another by a resistance 8|. A resistance 82 is connected in shunt to the choke coil 68. 48 and 4-9 have a ground connection 83. The cathode 59 is connected to the ground through the conductor 10 and a condenser 84.

In the contemplated operation of the control system shown in Fig. 5, the mutual inductance of the coils 48 and 49 will have a maximum value when the vane 40 is entirely withdrawn from the space between the coils, and will decrease as the vane is moved into said space, and will be substantially eliminated when the vane is within and extends through the space directly between the coils. For the contemplated use of the control system also, the constants of the system are selected in accordance with well known priciples so that when the vane is entirely withdrawn from the space between the control coils and their mutual inductance has its maximum value, the tetrode valve will oscillate with a high frequency. Said valve will oscillate with a progressively diminshing frequency, as the vane 48 is moved to progressively diminish said mutual inductance, until the latter is reduced to a certain critical low value. When that value is attained. the oscilla- The connected terminals of the coils tion of the tube is interrupted and will not be resumed until the mutual inductance is increased above said critical value.

When the tetrode valve is in oscillation, the average potential of the control grid 81 and the average current flow through the relay coil H are each lower than when the valve is not oscillating. In consequence, adjustments of they vane 48 vary the energizing current fiow through the differential relay coil II. The current flow through the relay coil 18 is not significantly eilected'by the oscillation or non-oscillation of the tetrode valve. In the normal operation of the apparatus shown in Fig. 5, the relay I2 is operatively energized by the current fiow through the winding 18 when the tetrode is oscillating and the current flow through the relay winding Ii is correspondingly low. When the oscillation of the tetrode is interrupted, the current fiow in the coil H increases sufiiciently to neutralize the relay energizing action of the winding 18.

The energization of the relay 1! raises an armature switch contact 88 and thereby connects a control conductor 88 to a control conductor terminal or contact". The deenergization of the relay permits the armature switch contact 88 to drop and disconnect the contact 81 from the conductor 88, and connect the latter to another control conductor terminal or contact 88. The connection of the control conductor 88 to the contact 81 is adapted to produce a control action in one direction, or sense, and the connection ofthe control conductor 86 to the control contact 88 is adapted to produce a control action in the reverse direction, or sense.

For example, the system shown in Fig. 5 may be employed to effect an on-ofi control of the supply of heat to a furnace, as an instrument responsive to furnace temperature deflects the vane 40, respectively into and out of the position in which it permits or prevents the oscillation of the tetrode and energization of the relay 12. In such case the connection of the control conductors 86 to the contact 81, and the connection of the conductor 88 and contact 88 may operate to turn the heat supply to the furnace on and 01!. respectively, in any one of various well known modes. Those modes need not be described, particularly as the control system arrangement shown in Fig. 5 forms no part of the present invention.

The relay 1! shown in Fig. 5 and the similar relays i2 and 12A shown in Figs. 6-8 are of a known commercial type, each comprising three contact finger 85' and moves the latter out of engagement with the contact finger 88 and into engagement with the contact finger 81.

While usable in other ways, the instrument features shown in Figs. 1-4 are especially well adapted for use in a control system of the character shown in Fig. 5, because of the relative simple and inexpensive character of such a system, and the ease with which the instrument may be adjusted to vary the value of the con- 8 trolling quantity required to exact 'a particular corrective control action.

In an electronic control system of the, character shown in Fig. 5. the oscillation of the tetrode may be initiated or terminated by a very small movement of the portion of the edge of the vane then adjacent the axis of the coils 88 and 88. In practice that movement need not be greater than about one thousandth of an inch. That movement may be eii'ected by a very small turning movement of the arm 44. As will be apparent, the pinand slot connection l2, 48 between the vane support 88 and .the oscillating arm 84, permits the ratio of the angular movements of the vane and arm 48 to be very high when the pin 48 intersects or is near the plane including the axes of the pivots 88 and 48, as they are shown in Fig. i.

The adjustment provisions shown in Figs. 2 and 3, constitute very simple, compact andeffective means for adjusting the control point of the instrument. When the control knob 21 is turned in the clockwise or counter clockwise direction as seen in Figs. 1 and 2, the effect is to lower or raise the link H. The link may thus be adjusted without any change in the value of the controlling quantity just as it would be adjusted by a change in the value of the controlling condition occurring while the knob is stationary.

As those skilled in the art will recognize, the fact that the internal gear segment 28 and link ll are raised and lowered by clockwise and counter clockwise knob movements, respectively,

rather than by reverse movements, of the knob 21, reduces the risk of maladjustments by an operator having little familiarity with the instrument. The fact that the roller or spur gear element 28 engages an edge 24 of the gear element 28, which is concave, results in an extension of the arc of contact of the two elements especially advantageous because the elements are less positively geared together by their coacting knurled surfaces than they would be if provided with the usual, and more expensively formed, out teeth.

When it may be found desirable in the initial calibration of the instrument, or in recalibrating it on a change in operating conditions, the coils 88 and 49 may be angularly adjusted about the axis of the clamping screw 52. The capacity for such adjustment permits the angular relation of the oscillating arm 84 and the vane'lil to be adjusted as required to obtain the desired speed relation between the turning movements of said arm and vane when the vane moves to initiate and interrupt the oscillation of the associated valve.

In Figs. 6 to 9, I have illustrated the use 0 the present invention in a control system especially devised to effect three position control, and including provisions for effecting definitely different control actions as the controlling quantity or condition attains predetermined diflerent values. The control system circuit network shown diagrammatically in Fig. 9, includes two units each of which is a duplicate of the single unit shown in Fig. 5. In Fig. 9 the various tube and circuit elements are designated by the reference numerals used in Fig. 5 to designate similar elements, but the letter A is added to the reference numerals of the right hand unit of Fig. 9, to avoid confusion in distinguishing between the elements of the two units.

In the arrangement collectively shown in Figs.

7 6 to 9, the control coils "and 49 of the left hand unit of Fig. 9 are carried by coil supports 50.

and their mutual inductance is controlled by a vane portion 40 carried by a vane element 35, as in the construction first described. The control coils 48A and 49A of the right hand unit are carried by. coil supports 50A and their mutual inductance is controlled by a vane 40A also carriedby the vane element 35. The two vanes 40 and 40A are parallel to one another, but their planes are displaced from one another in the direction of their common axis or supporting pivot To minimize risk of reactive interference by either unit with the control coils of the other unit, the conductors 63 and 56 of the left hand unit are connected to the supply conductors 64 and 55, respectively, while the conductors 63A and 66A0f the right hand unit are connected to the supply conductors 65 and 64, respectively. With the unit so connected to the alternating current supply conductors 64 and 65, the grid valve anode 59 of the left hand unit will be positive during half cycle periods alternating with those during which the anode 59A and right hand unit is positive.

With the vane and control coil arrangement shown dia rammatically in Fig. 9, the vane element occupies a "neutral position which is that shown in Fig. 9, when the value of the controlling condition is within a predetermined intermediate. or neutral, range of variation. In the neutral position of the vane element, the vane 40A extends into the space between the control coils 48A and 49A and so reduces the mutual inductance of those coils as to prevent oscillation at the right hand unit. and the vane 40 does not extend far enough into the space between the control coils 48 and 49 to reduce the mutual inductance of those coils sumciently to prevent the left hand unit from oscillating. When the vanes 40 and 40A are moved to the right as seen in Fi 9, into their low position. the mutual inductance of the coils 48A and 48B is increased so that oscillation will occur in the right hand unit as well as in the left hand unit. When the vanes are moved to the left from their position shown in Fig. 9. into their high posi ion, the mutual inductance of the coils 48 and 49 is reduced and the left hand unit as well as the right hand unit, is then prevented from oscillating.

The ener ization and deenergization of the relays 12 and 12A. efi'ected by initiating and interrupting the oscillations of the corresponding units, may be utilized to effect three position casing 31. In Figs. 6 and 8 the vane 40 is atcontrol of a regulating mechanism in various ways. As shown diagrammatically by way of iliustration and exam le in Fig. 9, the relay mechanism switches 85 and 85A are so associated with an ener izing control conductor E and with high, low and neutral control conductor terminals H, L and N. respectively, that when the vane element is in its high position and neither of the armature switches 85 and 85A is attracted by the corresponding relay, the energizing conducfor E is connected to the high control conductor terminal H. In such case, if the system be employed to control a furnace. the heat supply to the latter will be cut oil or reduced to a minibmum.v When the vane element is turned into its neutral position so that the left hand unit is set into oscillation. the armature 85 is attracted and thereby connects the energizing conductor E to the neutral control terminal N. When the vane tached to the side of the vane carrying element; 35 which is adjacent the mechanism casing 51A and the latter is provided with a short post 5| on which the coil supports for the coils 48 and 49 of the right hand unit are mounted. As shown the coils carried by the supports 50 are displaced clockwise about the axis of the pivot 36 from the coils carried by the coil supports 50A,

through an angle of about 30. The edge of the vane 40 entering the space between the coil supports 50, is also displaced in the clockwise direction from the edge of the vane 40A which enters the space between the coil supports 50A, but the displacement angle is smaller than 30.

The relative values of the two angles just mentioned determine the extent of angular movement of the vane supporting element 35. which occurs between the initiation or interruption of the oscillatory condition of the left hand unit of Flex. 9, and the initiation or interruption, respectively, of the oscillatory condition of the right hand unit. The extent of that angular movement determines the extent of the "neutral" range of variation of the controlling quantity, in which a change in said quantity produces no change The angular adiustment of the vanes 40 and 40A of Figs. 6 and 8 may be effected through, longitudinal adjustments of the link I! in response to variations in the value of the controlling quantity, exactly as adjustment is effected of the vane 40 of the instrument shown in Fig. 1. With control point adjustment means for the apparatus of Figs. 6, 8 and 9, like or analogous in operative results to the means shown in Figs. 1, 2 and 3, the permitted extent of the neutral range of variation 01' the controlling quantity depends wholly upon the displacement of the coils 48 and 49 from the coils 48A and 49A. In such case, the effect of a control point adjustment. is merely to vary the controlling quantity value at which oscillation of either unit of Fig. 9 is initiated or permitted. and to similarly vary the value of said quantity at which oscillation of the other unit is initiated and terminated. For many purposes, the adjustment of the three position control system and apparatus illustrated in Figs. 6 to 9,'which can be collectively effected by the angular adjustments oi the coil supports 50 and 50A and by a simple control point adjustment of the upper end of the link I! is entirely adequate.

In some cases, however, I may advantageously combine the apparatus shown in Figs. 6 to 8 in 74 a three position control instrument, with adjusta ienate ing provisions for the link II adapted to effect both control point adjustments and adjustments of the neutral range. Such an adjustable con nectlon between the links I] and I is illustrated in Figs. 10 and 11.

In the arrangement shown in Figs. 10 and 11, the links I6 is connected to an oscillating element ISA and turns the latter about its pivot ISA. The element ISA may be identical in substance with the element IS of the instrument shown in Fig. 1. As shown the element ISA includes an arm ISA which is connected to the link II by means quite difierent from those shown in Fig. 1 for connecting the arm I9 to the link II. The construction shown in Figs. 10 and 11 includes means resiliently holding the link II in a given median position when the value of the controlling quantity is within its neutral range of variation. To this end, the upper end of the link I1 is pivoted to the end of a control lever 96, pivoted at 97 and provided with a counter-weight 98. The latter is adapted to balance the weight of the lever 96, the link I1 and loadimpressed on the lower end of the latter.

The lever 96 is normally held in its neutral position by a spring I06 shown as acting on an arm 99 which is formed on said lever and which extends downwardly and terminates in a rearwardly extending part I00 (Fig. 12). Also pivoted on the shaft 91, which is attached to a frame member I02, is a second arm ml which has a portion parallel to the part I00 of the arm 99 and may be adjusted angularly about the shaft 91 of an eccentric pin I03. A pair of arms I04 and I05 are freely pivoted on the shaft 91 and are adapted to engage opposite sides of the parts I00 and IOI. These arms are resiliently pressed into engagement with the parts I 00 and IOI by means of the spring I06. The arrangement is such that the arms I04 and IOS are forced inwardly against the sides of parts I00 and IOI to maintain part I00 in line with part IOI and thereby hold the control lever 96 in its neutral position. Said neutral position can'be adjusted by rotating the eccentric pin and thereby angularly adjusting the arm IOI. The lever 96 is moved clockwise or counter-clockwise, as seen in Figs. and 11. against the opposing bias force exerted by the spring I06 whenever the value of the controlling condition rises above the upper limit, or falls below the lower limit, of the neutral range permitted by the adjustment of the apparatus.

The control lever 96 is moved out of its neutral position in the clockwise direction by means of a pin I0'I that projects from a differential lever I08 into the path of movement of a projection I09 formed on the lever 96, as is shown best in Fig. 13. This differential lever has its left end attached by a link IIO to the outer end of the arm I9A forming a part of the element ISA which turns about the pivot shaft ISA. The right end of the difierential lever I08 is pivoted at H2 to a sector member I I3. This member is pivoted on the frame member I02 at a point II4 approximately coaxial with the pivotal connection between link and lever 96. The sector member H3 is provided on its right end with spur gear teeth IIS which mesh with pinion H6.

The control lever 96 is moved in the counterclockwise direction by a pin III that projects from a second differential lever H8 and engages the lower side of a projection II9 on the control lever. The left end of the differential lever H8 is attached by a link SA to the arm I9A,

' and Ill be coaxial when the pins engage the upper and lower surfaces of projections I09 and 10 or to some other portion of the element ISA. The right end of lever H8 is pivoted at I20 to a member I2I that is also pivoted at H4. The left end of the member I2l is provided with ear teeth I22 that are engaged by a pinion I23. The projection I09 (see Fig. 13) from thelever 96 has its upper face slightly below the center of the differential lever 96 and is engaged by the pin I0'I. The projection II9 has its lower face slightly above the center of lever 96 and is engaged by the pin III. This arrangement permits an adjustment of the parts which will let pins I01 I I9, respectively.

In operation, the control lever 96 is maintained in its middle position by the spring I06 and the fingers I04 and I05, when the value of the controlling condition is within its neutral range, as is normally the case. As said value increases and decreases, the element ISA rotates counter-clockwise or clockwise and thus gives down and up movements, respectively, to the links H0 and IIOA. The up and down movements of the links III) and IIIIA give corresponding turning movements to the differential levers I08 and IIS around their respective pivots I I2 and I20. However, so long as the value of the controlling quantity remains within its neutral range, the turning movements of the levers I08 and H8 will not bring their projections I01 and Ill into operative engagement with the lever 96. In the neutral position of the lever 96, as previously stated, the energizing conductor E is connected to the neutral control terminal N.

When the valve of the controlling quantity increases above the upper limit of its neutral range, the resultant down movement of the lever I06 will cause its pin M1 to engage the projection I09 of the lever 96 and turn the latter clockwise and thereby lower the link I1 and give counter-clockwise adjustments to the vanes 40 and 40A. The effect of the adjustment thus given the vane 60 is to interrupt the oscillation of the left hand unit of Fig. 9 and to deenergize the relay I2. That connects the energizing conductor E to the high control terminal H, and thereby effects a control action which may well serve to return the controlling value to its neutral range. Conversely, when the value of the controlling condition falls below the lower limit of its neutral range, the pin I II of the differential lever .IIO engages the projection I09 of the lever 96 and turns the latter counter-clockwise. The resultant clockwise adjustment of the vane 40A permits the right hand unit of Fig. 9 to oscillate and thereby energizes the relay 12A, with the result of connecting the energizing conductor E to the low control terminal L. The effect of this may well serve to return the controlling valve to its neutral value.

In the arrangement shown in Fig. 11, the control parts are so relatively adjusted and disposed that in the neutral position of the lever 96 shown in that figure, the tube 55 valve 0. is not oscillating and the tube SSA valve a is oscillating. Advantageously and as shown, the relative positions of the vanes 40 and. 40A and the control coils respectively associated with those vanes, is. such that when the lever 96 is in its neutral condition only a small movement of the vane 40 in the clockwise direction is needed to interrupt the oscillation of the tube 55 valve a, and only a small movement of the vane 40A in the counter-clockwise direction is needed to initiate oscillation I range.

Menace of the valve a in the tube "A. In consequence; .a'slight angular adjustment of the lever 38 in either direction from the neutral position into which it is biased by the spring I03, initiates, or interrupts, oscillation of the valve a in one of the tubes, and eilects an abrupt change in the current flow through that valve. This contributes to the reliability and sharpness of the control action efiected when the value of the controlling quantity increases above the upper limit, or falls below the lower limit. of the neutral portion of the range of variation of said value in which changes do not effect control actions.

The adjustment provisions collectively shown in Figs. to 13 for determining what changes in the value of the controlling quantity shall produce angular adjustments of the controlling vanes 40 and 40A in one direction or the other, are useful in control apparatus differing from that disclosed and claimed herein, and are not my sole invention, but are the joint invention of Louis Gess and myself, and are fully disclosed and claimed in our Patent No. 2,386,108, issued October 2, 1945. However, special and peculiar advantages are obtained by the inclusion of such adjustment provisions in a control instrument in which an adjustment of the vane element away from its neutral position in either direction, initiates or interrupts the oscillation of an electronic control tube, because of the sharp and positive character of three-position control actions thereby made possible.

As will be apparent, the simultaneous adjustments of the controlling gears H3 and I23 in the directions required to similarly raise or to similarly lower the pins I01 and Ill carried by the levers I08 and H8, similarly change the control condition values at the opposite ends of the neutral range of variation of the controlling quantity, without varying the extent of that The arrangement shown in Figs. 10-13 12 can be eilected with the arrangement shown in Figs. 10-13 without corresponding variation in the range of adjustment of the vane element thus permits of the simple control point adiust-= merit results obtained by the use of the usual control point adjusting mechanism, ard obtain able by the use of the novel adjusting mechanism shown in Figs. 1, a and 5. As will be apparent, that mechanism might be employed to adjust either of the floating lever fulcrum members I63 and I2 I of Fig. 10, in lieu of the mechanism shown in Fig. 10 for adjusting those members.

In addition to the simple control point adjustments of the two members IE3 and I2I just described, the arrangement shown in Figs. 10-13 permits either of those members to be adjusted without a corresponding adjustment of the other member. Such an adjustment of one of the members H3 and I2I relative to the other, permits of the same sort of adjustment of the extent of neutral range of variation of the controlling quantity as may be efiected by the bodily adjustment toward or away from the other set of either of the two sets of control coils carried by the supports 50 and 50A shown in Figs. 6 and 8. This adjustment of the extent of the neutral range can be efiected, moreover, by rotatable adjusting elements accessible for adjustment rotation from the front of the instrument casing. Thus, as shown in Fig. 12, the gear I 23 of Fig. 10 may be angularly adjusted by the rotation of a knob I30 in front oi the frame plate I02 and carried by a shaft I3I extending through and journaled in said plate. The gear Ill of Fig. 10 may be adjusted through a similar knob and speed reducing gear arrangement. Furthermore, all of the above mentioned control point adjustments including vanes 40 and MIA, and therefore without any impairment of the operative capacity of that element to initiate or interrupt oscillation of one of the control tubes on a small movement of the current away from its neutral position in either direction.

The novel arrangement disclosed for varying the ratio of the angular movements of two oscillating elements, such as the arm 44 and member 35, as their angular positions are varied, may be used for control purposes very different from those hereinbefore specifically described. For example, the oscillation of the member 35 may be employed to mechanically adjust the position of a control element, such as a mercury switch, as is shown in Fig. 14. The arrangement shown in Fig. 14 comprises an arm 44 oscillated by longitudinal adjustments 0! link I! and carrying a pin 43 working in a slot 42 in the member 35, as in the constructions previously described. In the arrangement shown in Fig. 14 however, the controlling vane of the constructions previously described is replaced by an edge cam member I30.

The member, as shown, is a plate of sheet meta having a cam edge comprising three sections I3I, I32 and I33 angularly displaced from oneanother. Each of the cam edge sections I3I and I32 is an are extending circularly about the axis 36, but the radius of the arc IN is longer than the radius of the arc I32. The cam edge section I33 is intermediate and connects the sections I3I and E32. The angular adjustment of the cam member ltd adjusts a mercury switch I35 mounted in a carrier frame 635. The latter is pivoted to turn about an axis HE, and includes an arm I37 carrying a roller I33 which is held in engagement with the cam edge of the member I30 by a bias spring lot. When the roller I38 engages the cam edge section I3I, as shown in Fig. 14, the switch I3! is held in its open position. As the member 35 turns counterclockwise from the position shown in Fig. 14, until the roller I38 moves out of engagement with the edge section I3! and into engagement with the edge section I32, the bias spring I3t turns the action oi the bias sprin I39 into its closed position.

As shown, the closure of the switch I 3I closes a circuit including a source of current I40 and the winding of an electromagnetic valve I42 in a pipe Iti and. thereby opens said valve. A subsequent clockwise adjustment of the members 33 and I30 causing the roller I38 to move out of engagement with the cam edge section I32 and into engagement with the cam edge section I3l permits the valve It! to close. As will be apparent, the angular movement of the member I30 required to shift theswitch I34 between its closed and open positions depends upon the shape of the intermediate cam edge section I33. The novel means through which angular adjustment of the am it angularly adjusts the member 35 is especially advantageous in a control arrangement of the general character shown in Fig. 14, when the switch I34 or other control element is employed to effect on-ofl' control actions as a result of a very small angular adjustment of the arm 44. In the above mentioned Patent No. 2,386,108, the valve controlling arrangement shown in Fig. 14 is employed'for liquid level control purposes which need not be described herein.

In accordance with the provisions of the statlites, I have illustrated and described-the best forms of embodiment of my invention now known with a member deflecting in accordance with changes in the value of a controlling quantity, control mechanism actuated by the deflection of said member to produce a control efiect when said quantity attains a predetermined value, control point adjusting. means including an element angularly adjustable about an axis and varying said predetermined value by its angular adjustment, said element including a portion having a knurled concave edge extending circularly about said axis, and an adjusting part rotatable about a second axis parallel to the first mentioned axis and having a knurled surface surrounding said second axis and biased to engage and press against said concave edge and thereby operating, when rotated, to angularly adjust said element.

2. In a control instrument, the combination with a member deflecting in accordance with changes in the value of a controlling quantity, control mechanism actuated by the deflection of said member to produce a control efiect when said quantity attains a predetermined value, control point adjusting means including an element angularly adjustable about an axis and varying said predetermined value by its angular adjustment, said element including a portion having a knurled concave edge extending circularly about said axis, an adjusting part rotatable about a second axis parallel to the first mentioned axis and having a knurled surface surrounding said second axis and resilient supporting means for said second element pressing the latter against said concave edge so that said element is angularly adjusted when said adjusting part is rotated.

3. In a control system, the combination of two electronic valves, a deflecting element, means cooperating with said element to initiate and interrupt oscillation of one of said valves as said element deflects in a small deflection range, means cooperating with said element to initiate and terminate oscillation of the second of said valves as said element deflects in a second small deflection range, control means responsive to the changes in current flow through each of said valves produced by the initiation and interruption of its oscillation, mechanism responsive to changes in the value of a controlling quantity for deflecting said element through one of said ranges as said quantity varies in one value range and for deflecting said element through said second range as said quantity varies in a second value range different from the first mentioned value range, and means included in said mechanism adjustable to separately vary one limit or e ach of said value ranges.

4. In a control system the combination of two electronic valves, an element adapted to deflect in either direction away from an intermediate to initiate and interrupt oscillation of one of said valves as said element deflects in one direction or the other through a small deflection range mainly at one side of but including said intermediate position, means cooperating with said element to initiate and terminate oscillation of the second of said valves when said element deflects in one direction or the other through a second small range including said intermediate position but mainly at the side of the latter'opposite the first mentioned sides, control means responsive to the changes in current flow through each of said valves produced by the initiation and interruption of its oscillation, means responsive to changes in the value of a controlling quantityfor deflecting said element through one of said ranges as said quantity varies in cm range of its value and for deflecting said element through said second range as said quantity varies in a second-range of its value diflerent from the value range first mentioned, and adjusting means operable to separately vary the limit of each of said value ranges which differs least from the values in the other of said value ranges.

5. In a control system, the combination of two electronic valves, an element pivoted to turn about an axis in either direction away from an intermediate position, means cooperating with said element to initiate and interrupt oscillation of one of said valves as said element deflects in one direction or the other through a small deflection range mainly at one side of but including said intermediate position, means cooperating with said element to initiate and terminate oscillation of the second of said valves when said element deflects in one direction or the other through' a second small range including said intermediate position but mainly at the opposite side of the latter from the first mentioned side, bias means tending to maintain said element in said intermediate position, control means responsive to changes in current flow through each of said valves produced by the initiation and interruption of its oscillation, mechanism responsive to changes in the value of a control quantity including a member moving into and out of operative engagement with said element when said quantity exceeds a predetermined value and operatively engaging said element and deflectin the latter in one direction when the value of said quantity decreases below said predetermined value, a second member out of operative engagement with said element when the value of said quantity is less than a second predetermined value smaller than the first mentioned predetermined value and engaging and adjusting it in a direction opposite to said one direction when the value of said quantity rises above said second predetermined value, and adjusting means included in said mechanism for separately varying the said values of said quantity at which the two members respectively engage and deflect said element.

6. In a control instrument, the combination with a first member pivoted to turn about an axis and comprising an operating part displaced from said axis, of means responsive to changes in the value of a controlling quantity for angularly adlusting said member about said axis on and in accordance with a change in said value, a second member pivoted to turn through a predetermined range of adjustment about a second axis laterally displaced from the first mentioned axis and formed with an elongated guideway extending away from said second axis and receiving said position, means cooperating with said element :5 operating part whereby an angular movement or the first member effects an angular adjustment oi the second member varying rapidly as the distance of said part from said second axis varies. and regulating means comprising a regulating element having two regulating positions adiusted between said positions by the angular adjustment oi the said second member through a small portion of said range in which the distance or said part from said second axis is relatively small.

7. In a control instrument, the combination with a first member pivoted to turn about an axis and comprising an operating part displaced from said axis, of means responsive to changes in the value of a controlling quantity for angularly adjusting said member about said axis on and in accordance with a change in said value, a second member pivoted to turn through a predetermined range of adjustment about a second axis laterally displaced from the first mentioned axis and formed with an elongated guideway extending away from said second axis and receiving said operating part whereby an angular movement of the first member eilects an angular adjustment of the second member which varies rapidly as the distance of said part from said second axis varies, and regulating means comprising a twopositionregulating element adjusted between its two positions by said second member as the lat-- ter turns through a small portion only of its range a of adjustment.

EDWINC. BURDICK.

REFERENCES CITED The following references are of record in the ij'ile oi this patent:

STATES PATENTS 

